Does zero PSI make sense?

HarryL

I added a Wika 0-5 PSI gauge off of the pigtail servicing the pressuretrol. I cranked up the boiler and waited for my new Gorton #2s to close, and the steam to get to the radiators, but the gauge never moved off of zero. I opened the 15 psi emergency relief valve and heard what sounded like pressurized (albeit low pressure) steam escaping. Maybe for the test I need to set the tstat up a bunch so the boiler runs long enough to be sure all of the radiator vents are closed.

I went with a 0-5 as I was afraid that 0-3 would be too low if my pressuretrol wasn't working. Is 0-5 not sensitive enough, or is it reasonable for this gauge to sit at zero? Maybe a bum gauge?

Thanks,
Harry

David Nadle

The pressure may be more like 0.25 PSI until the system is full and all the valves close, which may be rarely. For this reason I prefer a 0-30 oz/in^2 gauge. But your gauge's max range should be higher than the pressuretrol max.

Fred

On a normal heat cycle, if your system is properly vented, it is not surprising that you didn't see any movement on a 0 - 5PSI gauge. I have a 0_ 3PSI gauge and I will see 1 ounce as we near the end of a heating cycle. Just make sure the pigtail you mounted it on is not plugged up with gunk. If it's clean, you should be good.

KC_Jones

Also the lower the pressure the faster the steam will move. The faster it moves the quicker you heat the less fuel you waste heating your home. I have a 0-15 ounce gauge and it basically just jiggles down below 1 ounce all the time. @ChrisJ has a very nicely tuned system. I can't remember his numbers, but he is very low.

ChrisJ

I have a -8" to +16" WC gauge now and it also barely moves. The most I've seen was 1" WC during a small recovery. Typical pressure is around 0.5"WC or 0.28 ounces.

Does zero psi make sense? To an extent, but it's more along the lines of your gauge is wrong for the system. I used to have a 0-3PSI Wika gauge but it never move. I have plans on putting the 3PSI gauge back on as I like to use it when testing the pressuretrol etc but I need to buy some fittings to make that happen and it's been a low priority.

HarryL

@ChrisJ - That is basically why I installed the 0-5 gauge, to see if the pressurtrol is doing its job. I have a new 0-4 vaporstat in the box. I'm trying to decide if I should keep the original pressurtrol or if I really need the vaporstat. I suppose I may not know until we get some colder weather up here in Boston.

Mark N

You're actually not at 0 PSI. The vents are at atmospheric pressure. When you start to make steam you are slightly above that and that is all it takes to move the steam out of the boiler. The steam moves on pressure differential. A fraction of a oz in good enough.

Fred

If you already have the Vaporstat, put it on. They are great for managing maximum pressures in ounces rather than pounds. Most of us who have installed them put them on a different tapping and pigtail on the boiler and we keep our Pressuretrol as well. They all get wired in series so that if the Vaporstat should ever fail, the pressuretrol will still kick in and stop the burner before pressures get to high. If you install the Vaporstat, set the Main to about 12 ounces and the Differential to 8 ounces. That will give you a Cut-in of 4 ounces and a Cut-out of 12 Ounces. Leave the Pressurestat set at Cut-in of .5PSI and Differential of 1PSI (for a Cut-out of 1.5PSI). Both of these devices are more for safety than anything else as 95% of the time the boiler never reaches a pressure sufficient to shut the boiler down on pressure but they may kick in on the few occassions when the weather is zero or below outside or you are recovering from a deep thermostat set-back of 4+ degrees (which you don't want to do regularly). You would have been good with a 0 - 3PSI gauge as you pressure should never get that high anyway.

David Nadle

If you really want to know what's going on with the pressure you can build a manometer for under $20 or buy a decent digital manometer for under $100.

To build a manometer buy a hose-to-barb fitting, some compatible clear tubing, and a yardstick. Attach the fitting to one end of about 7 or 8 feet of tubing and wrap some wire with a loop or hook around the other end. Connect the fitting end of the tubing to a boiler or wet loop drain. Let the tubing touch the floor and hang the open end as high as possible near the ceiling.

Open the drain and water will fill the tubing to match the boiler's water line. Tape the yardstick to the tubing so the water line is near the 8" mark. When you fire up the boiler, one PSI of pressure will raise the water column about 28". You can stand and watch the level and have a temporary gauge of -8 in. H2O vacuum to +28 in. H2O (1 PSI). Don't leave it unattended and be ready to kill the power if you are near to overflowing the tubing.

This could be useful in checking the calibration of an existing gauge, or deciding what range of gauge is appropriate.

PMJ

It is great to hear pressure controls on well run systems being referred to as Fred put it "safety devices". I have thought about my vaporstat as just that for a long time. When there is enough venting(nothing ever above atmospheric pressure in the way of the steam) many have observed that it takes only an ounce or two of steam pressure for it to move very swiftly down the mains.

KC points out that the lower the pressure the higher the speed. That is where just a little vacuum goes a long way. If just two ounces above atmospheric moves steam fast think of how fast it moves exploding out of the boiler into a piping system and rads at minus 25 ounces or so. I can tell you from experience it is much faster yet in those conditions. The dead men really knew what they were doing. Breathing back in and then having to push back out all that air on every cycle doesn't make a lot of sense. Especially those who have a 2 pipe system should really consider giving it a try.

Waterbury Steam

I rarely see more than 2 oz. unless recovering from a deep setback. If your system is maintaining temperature and all of the rads are heating, there's nothing to worry about. That is assuming that all of your traps/air vents are functioning properly and not leaking steam.

SWEI

PMJ said:

just a little vacuum goes a long way. If just two ounces above atmospheric moves steam fast think of how fast it moves exploding out of the boiler into a piping system and rads at minus 25 ounces or so. I can tell you from experience it is much faster yet in those conditions. The dead men really knew what they were doing. Breathing back in and then having to push back out all that air on every cycle doesn't make a lot of sense. Especially those who have a 2 pipe system should really consider giving it a try.

Once again, I'm very interested in developing a methodology for vacuum retrofits to existing 2-pipe steam systems. Any takers?

Eastman

@SWEI Did you see that Select Temp install manual that Gerry Gill posted? Although not a vacuum system I thought it had some relevant ideas.

SWEI

I've read it -- and found it quite interesting. Unfortunately, we have exactly zero prospects for installing new steam systems of any type here.

The potential to convert an existing two-pipe system to vacuum operation, increasing both comfort and efficiency, fits squarely into our business model. I'm still waiting for someone to tell me why this is not possible (or practical.)

PMJ

SWEI said:

I've read it -- and found it quite interesting. Unfortunately, we have exactly zero prospects for installing new steam systems of any type here.

The potential to convert an existing two-pipe system to vacuum operation, increasing both comfort and efficiency, fits squarely into our business model. I'm still waiting for someone to tell me why this is not possible (or practical.)

I'm not a contractor so I don't really know how practical it is on other 2 pipe systems. On mine, which was originally Mouat, there was very little to it. I inherited a system with vents on the main and dry return that hissed air on every cycle. There were cheap vents on about 1/2 the radiators. After reading about this I just decided to remove them all and go with only one vent on the dry return that I could be sure sealed for the vacuum. The original 1926 Mouat valves are on all the rads - I tightened a few that I could hear air leaking in on the off cycle but never replaced any. That's all I did as far as vacuum goes. There were no balancing issues. As I said before - a little vacuum goes a long way and doesn't need to last for hours. The value of the vacuum is when you are actually heating and cycling. I cycle more than most on purpose - to even things out.

Jamie Hall

I'm still thinking. Patience!

Eastman

@SWEI "methodology for vacuum retrofits"

Is there some specific problems you had in mind?

SWEI

The "problem" is clueless owners and contractors ripping perfectly good systems out because they don't understand them.

The opportunity would be the potential to improve both efficiency and comfort at a reasonable cost. I'm not talking about restoring an existing vapor system, but upgrading a standard two-pipe trap system. With the wealth of knowledge we have here I'm convinced it really should be workable.

Thanks Jamie, I'm looking forward to seeing what your ideas are.

Eastman

I kinda thinking along more technical lines -like balance, venting, etc.

PMJ

SWEI said:

The "problem" is clueless owners and contractors ripping perfectly good systems out because they don't understand them.

I think we have the government to thank for demise of steam in residential. Their efficiency rating system has seen to it that no new systems will be installed and therefore that no new blood will go into the trade.

That being said, Restoring existing systems to better operation sure would change some minds about steam. The trouble as I see it for a contractor is getting paid for the time required to observe a given system enough to fix things. As an owner/operator this is easy - even fun. But a contractor needs some time and the run of the house to really see what's up. I can see some resistance.

Anyway, I applaud your efforts. For what it is worth, I think that if any two pipe system originally installed with big enough piping that is insulated needs very few moving parts to run well.

jumper

A careful reading of LostArt suggests what can be done to go sub-atmospheric.First seal all vents to atmosphere.Test to see how airtight system is.On two pipe replace traps with orifices. Evacuate air and see what happens. It'll even work on one pipe if branches slope enough.See the Wilson patent on this site.

The paranoid part of me thinks that airless was severely discouraged by vent and trap vendors.

PMJ

jumper said:

A careful reading of LostArt suggests what can be done to go sub-atmospheric.First seal all vents to atmosphere.Test to see how airtight system is.On two pipe replace traps with orifices. Evacuate air and see what happens. It'll even work on one pipe if branches slope enough.See the Wilson patent on this site.

The paranoid part of me thinks that airless was severely discouraged by vent and trap vendors.

Again for what it's worth, Some of the original Mouat orifce traps had already been replaced with thermostatic traps so now I have a mix. Since I don't operate on pressure and never fill the rads none of the traps are really needed and never close anyway. I have not had any problem with either type running vacuum.

You may be right about the vent/trap vendors. Certainly what I have discovered at my place wouldn't be good for business.